In European Patent Specification WO 95/08055 the disclosure of which is herein incorporated by reference, there is described an internal combustion engine which utilizes a pivoted piston which rocks about a pivot point within a combustion chamber. The piston is connected adjacent the end of the piston remote from the pivot point to a connecting rod which drives a crankshaft. The piston has a first arcuate sealing surface to seal against a wall of the combustion chamber and a second sealing surface which is connected by a piston floor to the first arcuate sealing surface. Both sealing surfaces have a constant radial dimension from the pivot point of the piston.
The first arcuate sealing surface forms a skirt so a portion of the wall of the arcuate sealing surface will make a gas seal with the wall of the combustion chamber. The skirt also assists in dissipating heat in the piston. Adequate clearance between the outer surface of the piston and the chamber wall must be maintained to compensate for distortion that may occur through thermal expansion.
The piston also includes means to seal the sides of the piston against the combustion chamber walls and for this various forms of seals can be utilized. These are normally held in place either on the piston or in the wall of the combustion chamber by seal grooves into which the seal is located. Means are also provided to ensure the seals are correctly located in the grooves.
The prior art piston is generally manufactured in one piece and includes sealing grooves in the leading edge of the piston and in the sides of the piston and means are disclosed in WO95/08055 to enable adequate sealing of the piston against the walls of the combustion chamber to be obtained.